In a mobile communication system, when ciphering or deciphering is carded out at a transmission or reception side, the ciphering or deciphering result changes because of the existence of different parameters among ciphering or deciphering parameters.
Also, it is difficult or impossible to determine if the deciphered result is the same data as the original data or different data. Despite the different data, a UE forwards the different data to an application program, and an eNB forwards the different data to a Serving-Gateway (S-GW). The thus forwarded different data is discarded at the final user end.
In this ciphering/deciphering scheme, when one of the ciphering parameters changes due to the existence of internal or external errors, there is a problem that, because there is no restoration procedure until before the release of a corresponding radio bearer, erroneous packets can be continuously forwarded.
Accordingly, there is a need for a method and apparatus for, at ciphering/deciphering, restoring an error occurring because a ciphering parameter changes.
In a Long Term Evolution (LTE) system, a packet can be discarded when the packet is not transmitted during a predetermined time. A discard timer may be used for this function. The discard timer performs the function in a PDCP of a protocol stack. However, there is a problem that the current discard timer has no consideration for handover.
A UE can apply a discard timer for the same packet before and after the handover. However, an eNB has a problem that, when a serving, eNB changes before and after handover, a current serving eNB cannot use a discard timer used in an existing serving eNB. That is, in the current standard, there is a problem that, before and after handover and at non-occurrence of handover, there is no consistency in applying a discard timer to a downlink packet of an eNB.
In bad propagation environments, it can take much longer to transmit a packet, which has gone through a PDCP layer, through Radio Link Control/Media Access Control/Physical (RLC/MAC/PHY) layers than a maximum 1,500 milliseconds (ms) of a current discard timer. For example, when a Transmission Control Protocol (TCP) application program moves to a had location from a location of good propagation environments, a packet passes through a PDCP layer but the bad radio environments lead to an increase of a period of time for which the packet stands ready under an RLC layer as much as an increased window size.
When moving to a bad location from a situation in which a TCP window is increased in size (i.e., a location of good radio environments), there is a problem that, when a current discard timer value is ever used, many packets are discarded because of the expiration of a discard timer.
Also, in this situation, when the discard timer value is used limitless, there is a problem that it is difficult or impossible to control packet transmission using the discard timer in an eNB and a UE.